The invention relates to swinging hammers for material reducing machines and, more particularly, to a swinging hammer having an aggressive tooth for enhancing the operation and efficiency of a material reducing machine.
Changes in legislation and the scarcity of land suitable for use as landfills have led to an increase in the use of material reducing machines. Such machines are either of the forced feeding type or the gravity feeding type. In the forced feeding type, a conveyor is used to feed the input material into a rotating hammer mill or chipping rotor. Frequently, a hold-down mechanism is used to assist in the positive feeding of material into the hammer mill or rotor.
In the gravity feeding type, the hammer mill or rotor is positioned at the bottom of an open-topped container or tub. Material to be processed by the machine is dumped into the tub where gravity, perhaps assisted by oscillatory movement of the tub, will feed the material into the hammer mill or rotor.
To achieve a desired high output, and because of the wide variety of materials that must be processed by these material reducing machines, the hammer mills or rotors must be very heavily constructed to provide the necessary strength for effective operation and durability. Additionally, a heavy hammer mill or rotor will also have a large amount of angular momentum and energy to effectively process tough, high strength materials such as metals and also maintain a relatively constant rotational speed, resulting in less wear on the drive train and engine.
The heavy construction and severity of operating conditions have limited the variety of hammer designs that have been used. In forced feeding type material reducing machines, the cutting tools are typically fixed to the periphery with a rotating drum or disk. One problem associated with such machines is the loss or displacement of the chipping tools. Because of the high rates of rotation and impact energies, these displaced tools become high-velocity projectiles and are a serious safety concern. With forced-feeding type material reducing machines, however, the usual hold-down mechanism substantially overlies and covers the area from which such displaced tools would emerge. Additional shielding is easy to design into and build onto the machine to effectively contain any such displaced tools.
In gravity-fed machines, the containment for displaced cutting tools, or for high-velocity pieces of the materials being reduced, results from the walls of the tub and the volume of material filling the tub above the hammer mill. When the tub is close to empty, however, or if an open path to the exterior of the tub was otherwise extant, the possibility of a displaced tool or other high-velocity projectile being thrown out of the tub is possible. Heretofore, manufacturers have reduced this safety concern by using simple, block-shaped hammers that were generally larger in each principal dimension than a principal dimension of the materials being reduced. By using hammers lacking any narrow projecting portions, and avoiding add-on cutting tools, the likelihood of a catastrophic failure of a cutting member was greatly reduced.
Attempts have been made to improve the durability and efficiency of these block-shaped hammers. It is known, for example, to harden the edges of the tools with carbide. It is further known to shape a projecting leading edge on the hammer. Such hammers may either be asymmetrical, or of the common, reversible type having a profile known as bell-shaped. All such block-shaped hammers, even when hardened with carbide, have a relatively short surface life and a material reducing efficiency which falls off relatively quickly during use.